Thermal fog generators having internal combustion engines and liquid systems for introducing liquid into the hot engine exhaust gas to produce a vapor which, when dispensed into the atmosphere, condenses to form a fog are known prior art. Examples of this type of thermal fog generator are disclosed by Tenney in U.S. Pat. No. 3,205,176 and Scott in U.S. Pat. Nos. 3,607,780 and 4,155,249. The liquid formulations are stored in tanks and pressurized containers. The liquid in the tank of Tenney cannot be conveniently and quickly changed to a second liquid as the first liquid must be used up or drained and replaced with a second liquid. The handling of the liquid can result in spillage and contact with the operator's skin, which can cause serious chemical burns and/or poisoning. Needle valves used to regulate the rate of flow of fluid to the engine exhaust pipe are not intended to control the starting and stopping of fog generation. The liquid formulation in the pressurized container of Scott continues to flow after the engine stops, unless a separate manual valve is turned off. In the event the manual valve is not turned off, liquid formulation will flow from the generator. This can cause hazards to the operator and environment.
Portable leaf blowers having small internal combustion engines driving a rotatable air blower are used to provide a continuous air stream to remove objects, trash, leaves, and the like from lawns. These blowers may be hand-held and lightweight machines, which are carried by the operator in use. These blowers have not been equipped with fog and smoke generating systems operable to dispense fogs and smoke into the atmosphere.